Transdermal drug delivery systems have, in recent years, become an increasingly important means of administering drugs and like therapeutic agents.
Presently, there are two types of transdermal drug delivery systems, i.e., "Passive" and "Active." Passive systems deliver drug through the skin of the user unaided, an example of which would involve the application of a topical anesthetic to provide localized relief, as disclosed in U.S. Pat. No. 3,814,095 (Lubens). Active systems on the other hand deliver drug through the skin of the user using, for example, iontophoresis, which according to Stedman's Medical Dictionary, is defined as "the introduction into the tissues, by means of an electric current, of the ions of a chosen medicament." Such systems offer advantages clearly not achievable by any other methods of administration, such as avoiding introduction of the drug through the gastro-intestinal tract or punctures in the skin to name a few.
Conventional iontophoretic devices, such as those described in U.S. Pat. No. 4,820,263 (Spevak et al.), U.S. Pat. No. 4,927,408 (Haak et al.) and U.S. Pat. No. 5,084,008 (Phipps), the disclosures of which are hereby incorporated by reference, for delivering a drug or medicine transdermally through iontophoresis, basically consist of two electrodes, which are in contact with a portion of a patient's body. A first electrode, generally called the active electrode, delivers the ionic substance or drug into the body by iontophoresis. The second electrode, generally called the counter electrode, closes an electrical circuit that includes the first electrode and the patient's body. Generally, the circuit includes a source of electrical energy, such as a battery. The ionic substance to be driven into the body may be either positively charged or negatively charged. In the case of a positively charged ionic substance, the anode of the iontophoretic device becomes the active electrode and the cathode serves as the counter electrode to complete the circuit. Alternatively, if the ionic substance to be iontophoretically delivered is negatively charged, the cathode will be the active electrode and the anode will be the counter electrode.
In practice, this process is typically achieved by placing the ionic drug either in solution or in gel form on a carrier and placing the drug-containing carrier, for example, in the form of a drug-filled adhesive patch, into contact with the skin. The pair of electrodes is placed in contact with the skin and with the carrier. Direct current is applied between the two electrodes. Under the influence of the electric field present, the drug molecules migrate through the skin. As current flows between the two electrodes placed at spaced apart locations on the skin, the current path carries the drug with it.
However, problems and limitations have been associated with prior devices, particularly with respect to storing and/or dispensing patches for use with reusable controllers and the like. In addition, there has been a problem associated with disposal of used patches, which may contain some unused quantity of the drug.
Thus, there has been a need for an iontophoretic drug delivery system, including a unit for dispensing and/or collecting patches, which would eliminate the problems and limitations associated with the prior devices discussed above, most significant of the problems being associated with dispensing patches for use with reusable controllers and for collecting used patches.